This invention relates generally to the field of dispenser devices used to introduce into a flowing liquid small quantities of a chemical solution created by dissolving a solid or granular chemical. More particularly, the invention relates to such devices to be used as a component in water circulation or supply systems, where the rate of introduction of the dissolved chemical into the water is controlled in a manner related to the flow volume of the water stream to insure proper concentration percentage. Even more particularly, the invention relates to replaceable dispensing means which comprise a cartridge which contains the solid chemical and are retained within a housing, where the dispensing means is utilized with in-line or uni-directional flow housings.
It is desirable or necessary in many water supply or recirculation systems, such as water for household or industrial use, or water for use in spas and pools, to add certain chemicals to the water to control bacteria or fungal growth, corrosion, scale deposits, etc. Commonly known additives include chlorine, polyphosphate or sodium silicate. Such additives are typically supplied in solid or granular form for ease of handling, and must therefore be dissolved in liquid to create a solution then introduced into the water flow. It is imperative that the chemical additives be supplied in the proper concentration, and it is important that the mechanism for adding the chemical solutions provide for proper rate introduction with little variation in concentration. Many conventional systems fail these criteria, the mechanisms being unable to prevent variations in concentration and introduction rates, especially in circumstances where the water flow is not continuous and varies in pressure.
The most simplistic solid chemical additive mechanisms simply divert all or a portion of the water flow stream through a container holding the solid chemical. The water flowing from the container will then include an amount of dissolved chemical. These devices suffer from lack of dispensing control, since the amount of chemical present in the outflow is dependent on the volume of solid chemical in the container. As that volume decreases, the concentration of dissolved chemical in the outflow also decreases. Additionally, this type of system produces a highly concentrated chemical surge when water flow is resumed after being shut off for a period of time. Finally, variation in the water flow rate will not correspondingly alter the dissolving rate of the chemical, producing incorrect concentration amounts in the outflow.
Attempts have been made to develop a mechanism which addresses the problems encountered in correctly metering and controlling the chemical introduction and concentration rates, but known systems are either overly complicated or do not fully solve all the problems set forth above. A complicated mechanism is described in U.S. Pat. No. 4,780,197 to Schuman, which discloses a flow-through chemical dispenser cartridge positioned within the internal core of a filter which requires one or more operational valves to perform effectively. A more simplified approach is shown in U.S. Pat. No. 4,347,224 to Beckert et al. This patent discloses a flow housing which contains an internally mounted chemical cartridge. A small amount of the water flow is diverted into the bottom of the chemical cartridge and the chemical solution is drawn through a small aperture in the top of the cartridge by the pressure differential created by the flow of the bulk of the water passing through the housing. This apparatus provides a simple approach to solving the problems encountered in standard solid chemical systems, but the mechanism is just a variation of the standard system where a portion of the water stream is passed through the solid chemical before being returned to the main flow stream. The distinction in Beckert et al. is that the cartridge containing the solid chemical is mounted within a large housing through which all the water flows. The sizing of the cartridge is such to create an annular passage down to the bottom of the chemical cartridge, where the water flows through a plurality of liquid inlet holes, past the chemical and out the liquid outlet hole. In effect, the annular passage is just a substitute for a small bypass conduit as found in many old systems, and the problems associated with variations in concentration and surging would still be present.
A much improved design and construction for a flow-through chemical dispenser is shown in my U.S. Pat. No. 5,580,448, wherein a unique cartridge configuration is used to correctly meter and control the chemical introduction and concentration rates of the dissolved solid chemical into the liquid flow stream. The dispenser unit has an upper base member with inlet and outlet openings, and a depending housing is threaded onto the base. A dispenser means comprising an upper tube, an apertured midsection and a cartridge containing the solid chemical is coaxially mounted within the housing, such that water flows through an annular filter, into flow openings in the apertured midsection above the cartridge and out from the top of the upper tube. While the dispenser unit functions at optimum efficiency, the design of the dispenser means is limiting in that particular flow paths are dictated by the housing structure.
It is an object of this invention to provide a dispenser device which provides a steady state concentration of dissolved chemical, which introduces the chemical solution into the main water stream in amounts directed related to water flow rate or volume to maintain precise percentages of chemical solution, which does not produce excessive chemical concentration during periods of no water flow, and which does not introduce excessive amounts of dissolved chemical when water flow is resumed. It is an object to provide such a device where the cartridge containing the solid chemical is not a flow through cartridge, such that water is not passed through the solid chemical. It is an object to provide such a device where the chemical cartridge can be used alone or in combination with a filter or other treating media. It is an object to provide such a device where the dispenser device containing the dispenser means is an in-line or unidirectional flow dispenser.